1. Field of the Invention
The present invention relates to a pump for an inkjet printer, and more particularly, to a pump for an inkjet printer which squeeze a tube to generate a suction force, thereby sucking ink from an inkjet head nozzle.
2. Description of the Related Art
An inkjet printer using a permanent head, which can be permanently used and refilled (replenished) with ink, and a semi-permanent head, generally includes a pump. The pump for the inkjet printer performs a sucking operation in order to remove air that may enter during the replenishing of the ink and to open a head nozzle when the head nozzle is blocked by dried ink.
Pumps used in inkjet printers are generally divided into piston type pump apparatuses and rotor type pump apparatuses. The rotor type is more commonly used. The rotor type utilizes the rotation of a rotor to squeeze a plastic tube and thus generate a pressure difference which causes ink to be ejected from an inkjet head nozzle.
Several inventions relating to such a rotor type pump apparatus have been patented and have been put to practical use, one example of which is disclosed in U.S. Pat. No. 5,910,808. Operation of that pump apparatus as disclosed will be briefly described with reference to FIG. 1.
As a rotor of the pump apparatus rotates in a counterclockwise direction, a roller 14 squeezes a tube 10. Due to a pressure difference to an atmosphere pressure occurring as the tube 10 is squeezed, the squeezing results in a negative pressure differential relative to the ambient. This negative pressure differential causes ink in an inkjet head nozzle (not shown) to be sucked into the tube 10 an end of which is connected to the inkjet head nozzle.
After the suction of the ink, when the rotor rotates in a clockwise direction, the roller 14 comes into contact with a damper plate 16 made of rubber as shown in FIG. 2. This contact moves the roller inward along a cam groove 12. In this state, the roller 14 does not squeeze the tube 10 so as to allow the tube 10 to return to its original (i.e. uncompressed) state. That is, the conventional rotor type pump apparatus varies the position of the roller 14 within the cam groove 12 by using the damper plate 16 when the rotor is rotated in the counterclockwise and the clockwise directions, whereby the tube 10 is squeezed and relaxed and thus the sucking operation is performed.
However, since in the conventional rotor type pump apparatus the position of the roller 14 is changed within the cam groove 12 by using the rubber-made damper plate 16 when the tube 10 is contracted and relaxed, the damper plate 16 is periodically subjected to an alternate shock load. Accordingly, when the pump apparatus is used for a long time, the properties of the rubber-made damper plate 16 such as elasticity and surface friction coefficient are deteriorated and thus reliability of the sucking operation is reduced.
Also, the collision of the roller 14 with the damper plate 16 when the damper plate 16 changes the position of the roller 14 in the cam groove 12 causes noise. When the tube 10 is disposed on a right-angled wall, the rotation of the roller 14 causes the tube 10 to ascend.
Still further, since the conventional pump apparatus requires many parts such as a plurality of gears, the damper plate, and the like manufacture and/or assembly can be complicated.